Diamond Fluorescence

When we speak of Diamond Fluorescence, we are referring to the diamonds tendency to emit a soft colored glow when subjected to ultraviolet light (such as a “black light”).

Before going into the details of fluorescence, here’s our overall opinion:
the simple existence or absence of fluorescence should not influence your decision to purchase a diamond.

Diamond Fluorescence is a hotly debated topic in the diamond industry, but a 1997 study by the GIA suggests fluorescence makes very little difference to the appearance of the diamond.

In the diamond industry, the existence of fluorescence in a diamond (caused by the natural mineral properties of the diamond), has caused many debates and has, in many instances, influenced the pricing of diamonds.

Natural Light

Ultraviolet Light

It is common to find that diamonds with colorless grades (D-E-F) or near colorless grades (G-H-I-J) are lower in price when they exhibit fluorescence and faint yellow grades (K-L-M) are higher in price when exhibiting fluorescence.

The “theory” has been that: 1) fluorescence has a negative impact on colorless diamonds (making them appear cloudy) and 2) a positive impact on faint yellows (blue fluorescence supposedly counter-balancing the yellow color and making the diamond appear whiter).

Given the results of a 1997 GIA study on the effect of ultraviolet fluorescence on a diamond’s appearance, we tend to toss the first half of that theory out the window and give slightly less credence to the second half.

The GIA study selected a group of similarly graded diamonds with varying degrees of fluorescence to be observed and commented on by study participants. Participants in the study included: trained diamond graders, trade professionals (e.g., jewelers), and average observers (general jewelry buying public).

Here’s a quote from the study:

“For the average observer, meant to represent the jewelry buying public, no systematic effects of fluorescence were detected. Even the experienced observers did not consistently agree on the effects of fluorescence from one stone to the next.

“In general, the results revealed that strongly blue fluorescent diamonds were perceived to have a better color appearance when viewed table-up [ed: right-side up, as when placed in a setting] with no discernible trend table-down [ed: upside-down]. Most observers saw no relationship between fluorescence and transparency.”

In other words, for the average observer fluorescence made no difference and experienced observers (diamond graders and trade professionals) did not agree on the influence of fluorescence. And contrary to previous theories, the experienced/trained observers most consistently determined that diamonds with strong fluorescence were the ones with the best color.

Bottom Line on Fluorescence

If industry experts can’t agree on the influence of flourescence and constantly split hairs over its effect, we feel it falls into the range of minutiae that simply serves to confound and confuse, rather than inform the diamond buying public.

However, because of industry debate and prejudice (which appears unfounded), you may find colorless or near-colorless diamonds that exhibit fluorescence have slightly lower prices than those that do not. Our opinion? Enjoy the lower price.

Of course, if you are buying diamonds as an investment and intend resale, you’ll want to pay attention to how the industry prices diamonds with fluoresence — independent of whether the price difference is justified.